/Engine/Source/Runtime/UMG/Public/Blueprint/WidgetTree.h
Attempts to move a constructed Widget to another tree. Returns true on a successful move.
static bool TryMoveWidgetToNewTree ( [UWidget](API\Runtime\UMG\Components\UWidget) * Widget, [UWidgetTree](API\Runtime\UMG\Blueprint\UWidgetTree) * DestinationTree )